Fair Value Measurements (Gains (Losses) from Loans Held-for-Sale Included in the Consolidated Statements of Income) (Details) - Loans held for sale - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total included in earnings	$ 34,989	$ 17,331	$ 6,376
Interest income
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total included in earnings	2,540	1,606	83
Net gain (loss) on sale of loans and other mortgage banking revenue
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total included in earnings	715	39	(61)
Net gain on sales of loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total included in earnings	$ 31,734	$ 15,686	$ 6,354